Malaria affects over 200 million individuals annually, resulting in 800,000 fatalities. Current tests use blood smears and can only detect the disease when 0.1-1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as β-hematin was derived from porcine haemin. The specific purpose of this study is to establish the efficacy of using β-hematin, rather than hemozoin, for photoacoustic measurements. We characterized β-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that β-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm(-1). Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the β-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection.

中文翻译：

---

β-血红素的光声光谱

疟疾每年影响超过 2 亿人，导致 80 万人死亡。目前的测试使用血液涂片，只有在 0.1-1% 的血细胞被感染时才能检测到疾病。我们正在研究使用光声流量计检测 1000 万或更多正常血细胞中只有一个受感染的细胞，从而在患者出现症状之前诊断感染。光声流量计类似于传统的流式细胞仪，不同之处在于稀有细胞被纳秒激光脉冲靶向以诱导超声响应。该系统已用于检测 10 ml 血液中的单个黑色素瘤细胞。我们的目标是应用光声流量计来检测疟疾色素血红素，它是血液中寄生虫消化的血红蛋白的副产品。然而，血红素难以纯化超过 1 毫克的量，因此一种合成类似物，称为 β-血红素是从猪血红素中提取的。本研究的具体目的是确定使用 β-血红素而不是血红素进行光声测量的功效。我们使用紫外-可见光谱、TEM 和 FTIR 对 β-血红素进行了表征，然后测试了激光照射对合成产物的影响。我们最终使用光声激发确定了它的吸收光谱。紫外-可见光谱证实β-血红素与其前体明显不同。TEM 分析证实了其先前建立的纳米棒形状，将 FTIR 结果与已发布的光谱数据进行比较表明，我们的产品在 1661 和 1206 cm(-1) 处具有独特的吸收峰。还，我们的研究表明，长时间的照射会显着改变 β-血红素的物理和光学特性，导致在较短波长下的吸收增加。尽管如此，光声吸收光谱模拟了紫外-可见光谱产生的吸收光谱，这证实了光声方法的准确性，并强烈表明光声流量计可用作诊断疟疾感染的工具。